Histological improvements following energy restriction and exercise: The role of insulin resistance in resolution of MASH

Abstract

Background & aims: Metabolic dysfunction-associated steatohepatitis (MASH) is one of the most common liver diseases worldwide and is characterized by multi-tissue insulin resistance. The effects of a 10-month energy restriction and exercise intervention on liver histology, anthropometrics, plasma biochemistries, and insulin sensitivity were compared to standard of care (control) to understand mechanisms that support liver health improvements.

Methods: Following medical diagnosis of MASH, individuals were randomized to treatment (n = 16) or control (n = 8). Liver fat (magnetic resonance spectroscopy), 18-hour plasma biochemical measurements, and isotopically labeled hyperinsulinemic-euglycemic clamps were completed pre- and post-intervention. Body composition and cardiorespiratory fitness (VO₂peak) were also measured mid-intervention. Those in the treatment group were counseled to reduce energy intake and completed supervised, high-intensity interval training (3x/week) for 10 months. Controls continued physician-directed care.

Results: Treatment induced significant (p <0.05) reductions in body weight, fat mass, and liver injury, while VO₂peak (p <0.05) and non-esterified fatty acid suppression (p = 0.06) were improved. Both groups exhibited reductions in total energy intake, hemoglobin A1c, hepatic insulin resistance, and liver fat (p <0.05). Compared to control, treatment induced a two-fold increase in peripheral insulin sensitivity which was significantly related to higher VO₂peak and resolution of liver disease.

Conclusions: Exercise and energy restriction elicited significant and clinically meaningful treatment effects on liver health, potentially driven by a redistribution of excess nutrients to skeletal muscle, thereby reducing hepatic nutrient toxicity. Clinical guidelines should emphasize the addition of aerobic exercise in lifestyle treatments for the greatest histologic benefit in individuals with advanced MASH.

Impact and implications: The mechanisms that underpin histologic improvement in individuals with metabolic dysfunction-associated steatohepatitis (MASH) are not well understood. This study evaluated the relationship between liver and metabolic health, testing how changes in one may affect the other. We investigated the effects of energy restriction and exercise on the association between multi-tissue insulin sensitivity and histologic improvements in participants with biopsy-proven MASH. For the first time, these results show that an improvement in peripheral (but not hepatic) insulin sensitivity and systemic markers of muscle function (i.e. cardiorespiratory fitness) were strongly related to resolution of liver disease. Extrahepatic disposal of substrates and improved fitness levels supported histologic improvement, confirming the addition of exercise as crucial to lifestyle interventions in MASH.

Clinical trial number: NCT03151798.

Keywords: MASH; MASLD; NAFLD; energy restriction; exercise; histology; insulin resistance; lifestyle treatment.